ldrdf.c

一个汇编语言编译器源码

	    {
                /* we're only interested in exports, so skip others: */
		if (hr->type != 3) continue; 

		/*
		 * Find the symbol in the symbol table. If the symbol isn't
		 * defined, we aren't interested, so go on to the next.
		 * If it is defined as anything but -1, we're also not
		 * interested. But if it is defined as -1, insert this
		 * module into the list of modules to use, and go
		 * immediately on to the next module...
		 */
		if (! symtab_get(hr->e.label, &segment, &offset) 
		    || segment != -1)
		{
		    continue;    
		}
		
		doneanything = 1;
		keepfile = 1;

		/*
		 * as there are undefined symbols, we can assume that
		 * there are modules on the module list by the time
		 * we get here.
		 */
		lastmodule->next = malloc(sizeof(*lastmodule->next));
		if (!lastmodule->next) {
		    fprintf(stderr, "ldrdf: not enough memory\n");
		    exit(1);
		}
		lastmodule = lastmodule->next;
		memcpy(&lastmodule->f, &f, sizeof(f));
		lastmodule->name = strdup(f.name);
		processmodule(f.name, lastmodule);
		break;
	    }
	    if (!keepfile)
		rdfclose(&f);	    
	}
	if (rdl_error != 0 && rdl_error != RDL_ENOTFOUND)
	    rdl_perror("ldrdf", cur->name);
	cur = cur->next;
    }

    return doneanything;
}

/*
 * write_output()
 *
 * this takes the linked list of modules, and walks through it, merging
 * all the modules into a single output module, and then writes this to a
 * file.
 */
void write_output(const char * filename)
{
    FILE          * f = fopen(filename, "wb");
    rdf_headerbuf * rdfheader = rdfnewheader();
    struct modulenode * cur;
    int		  i, availableseg, seg, localseg, isrelative;
    void	  * header;
    rdfheaderrec  * hr, newrec;
    symtabEnt 	  * se;
    segtab	  segs;
    long	  offset;
    byte 	  * data;

    if (!f) {
	fprintf(stderr, "ldrdf: couldn't open %s for output\n", filename);
	exit(1);
    }
    if (!rdfheader) {
	fprintf(stderr, "ldrdf: out of memory\n");
	exit(1);
    }

    if (options.verbose)
	printf ("\nbuilding output module (%d segments)\n", nsegs);
    
    /*
     * Allocate the memory for the segments. We may be better off
     * building the output module one segment at a time when running
     * under 16 bit DOS, but that would be a slower way of doing this.
     * And you could always use DJGPP...
     */
    for (i = 0; i < nsegs; i++)
    {
	outputseg[i].data = malloc(outputseg[i].length);
	if (!outputseg[i].data) {
	    fprintf(stderr, "ldrdf: out of memory\n");
	    exit(1);
	}
    }

    /*
     * initialise availableseg, used to allocate segment numbers for
     * imported and exported labels...
     */
    availableseg = nsegs;

    /*
     * Step through the modules, performing required actions on each one
     */
    for (cur = modules; cur; cur=cur->next)
    {
	/*
	 * Read the actual segment contents into the correct places in
	 * the newly allocated segments
	 */

	for (i = 0; i < cur->f.nsegs; i++)
	{
	    int dest = cur->seginfo[i].dest_seg;

	    if (dest == -1) continue;
	    if (rdfloadseg(&cur->f, i, 
			   outputseg[dest].data + cur->seginfo[i].reloc))
	    {
		rdfperror("ldrdf", cur->name);
		exit(1);
	    }
	}
 
	/*
	 * Perform fixups, and add new header records where required
	 */

	header = malloc(cur->f.header_len);
	if (!header) {
	    fprintf(stderr, "ldrdf: out of memory\n");
	    exit(1);
	}

	if (cur->f.header_loc)
	    rdfheaderrewind(&cur->f);
	else
	    if (rdfloadseg(&cur->f, RDOFF_HEADER, header))
	    {
		rdfperror("ldrdf", cur->name);
		exit(1);
	    }
	
	/*
	 * we need to create a local segment number -> location
	 * table for the segments in this module.
	 */
	init_seglocations(&segs);
	for (i = 0; i < cur->f.nsegs; i++)
	{
	    add_seglocation(&segs, cur->f.seg[i].number,
			    cur->seginfo[i].dest_seg, cur->seginfo[i].reloc);
	}
	/*
	 * and the BSS segment (doh!)
	 */
	add_seglocation (&segs, 2, 2, cur->bss_reloc);

	while ((hr = rdfgetheaderrec(&cur->f)))
	{
	    switch(hr->type) {
	    case 1: /* relocation record - need to do a fixup */
		/*
		 * First correct the offset stored in the segment from
		 * the start of the segment (which may well have changed).
		 *
		 * To do this we add to the number stored the relocation
		 * factor associated with the segment that contains the
		 * target segment.
		 *
		 * The relocation could be a relative relocation, in which
		 * case we have to first subtract the amount we've relocated
		 * the containing segment by.
		 */
		
		if (!get_seglocation(&segs, hr->r.refseg, &seg, &offset))
		{
		    fprintf(stderr, "%s: reloc to undefined segment %04x\n",
			    cur->name, (int) hr->r.refseg);
		    errorcount++;
		    break;
		}

		isrelative = (hr->r.segment & 64) == 64;
		hr->r.segment &= 63;

		if (hr->r.segment == 2 || 
		    (localseg = rdffindsegment(&cur->f, hr->r.segment)) == -1)
		{
		    fprintf(stderr, "%s: reloc from %s segment (%d)\n", 
			    cur->name,
			    hr->r.segment == 2 ? "BSS" : "unknown",
			    hr->r.segment);
		    errorcount++;
		    break;
		}

		if (hr->r.length != 1 && hr->r.length != 2 && hr->r.length!=4)
		{
		    fprintf(stderr, "%s: nonstandard length reloc "
			    "(%d bytes)\n", cur->name, hr->r.length);
		    errorcount++;
		    break;
		}

		/* 
		 * okay, now the relocation is in the segment pointed to by
		 * cur->seginfo[localseg], and we know everything else is
		 * okay to go ahead and do the relocation
		 */
		data = outputseg[cur->seginfo[localseg].dest_seg].data;
		data += cur->seginfo[localseg].reloc + hr->r.offset;

		/*
		 * data now points to the reference that needs
		 * relocation. Calculate the relocation factor.
		 * Factor is:
		 *      offset of referred object in segment [in offset]
		 *	(- relocation of localseg, if ref is relative)
		 * For simplicity, the result is stored in 'offset'.
		 * Then add 'offset' onto the value at data.
		 */
		
		if (isrelative) offset -= cur->seginfo[localseg].reloc;
		switch (hr->r.length)
		{
		case 1:
		    offset += *data;
		    if (offset < -127 || offset > 128)
			fprintf(stderr, "warning: relocation out of range "
				"at %s(%02x:%08lx)\n", cur->name,
				(int)hr->r.segment, hr->r.offset);
		    *data = (char) offset;
		    break;
		case 2:
		    offset += * (short *)data;
		    if (offset < -32767 || offset > 32768)
			fprintf(stderr, "warning: relocation out of range "
				"at %s(%02x:%08lx)\n", cur->name,
				(int)hr->r.segment, hr->r.offset);
		    * (short *)data = (short) offset;
		    break;
		case 4:
		    * (long *)data += offset;
		    /* we can't easily detect overflow on this one */
		    break;
		}

		/*
		 * If the relocation was relative between two symbols in
		 * the same segment, then we're done.
		 *
		 * Otherwise, we need to output a new relocation record
		 * with the references updated segment and offset...
		 */
		if (! isrelative 
		    || cur->seginfo[localseg].dest_seg != seg)
		{
		    hr->r.segment = cur->seginfo[localseg].dest_seg;
		    hr->r.offset += cur->seginfo[localseg].reloc;
		    hr->r.refseg = seg;
		    rdfaddheader(rdfheader, hr);
		}
		break;

	    case 2: /* import symbol */
	    case 7:
		/*
		 * scan the global symbol table for the symbol
		 * and associate its location with the segment number 
		 * for this module
		 */
		se = symtabFind(symtab, hr->i.label);
		if (!se || se->segment == -1) {
		    if (options.warnUnresolved) {
			fprintf(stderr, "warning: unresolved reference to `%s'"
				" in module `%s'\n", hr->i.label, cur->name);
		    }
		    /*
		     * we need to allocate a segment number for this
		     * symbol, and store it in the symbol table for
		     * future reference
		     */ 
		    if (!se) {
			se=malloc(sizeof(*se));
			if (!se) {
			    fprintf(stderr, "ldrdf: out of memory\n");
			    exit(1);
			}
			se->name = strdup(hr->i.label);
			se->flags = 0;
			se->segment = availableseg++;
			se->offset = 0;
			symtabInsert(symtab, se);
		    }
		    else {
			se->segment = availableseg++;
			se->offset = 0;
		    }
		    /*
		     * output a header record that imports it to the
		     * recently allocated segment number...
		     */
		    newrec = *hr;
		    newrec.i.segment = se->segment;
		    rdfaddheader(rdfheader, &newrec);
		}

		add_seglocation(&segs, hr->i.segment, se->segment, se->offset);
		
		break;

	    case 3: /* export symbol */
		/*
		 * need to insert an export for this symbol into the new
		 * header, unless we're stripping symbols [unless this
		 * symbol is in an explicit keep list]. *** FIXME ***
		 */
		if (options.strip)
		    break;

		if (hr->e.segment == 2) {
		    seg = 2;
		    offset = cur->bss_reloc;
		}
		else {
		    localseg = rdffindsegment(&cur->f, hr->e.segment);
		    if (localseg == -1) {
			fprintf(stderr, "%s: exported symbol `%s' from "
				"unrecognised segment\n", cur->name,
				hr->e.label);
			errorcount++;
			break;
		    }
		    offset = cur->seginfo[localseg].reloc;
		    seg = cur->seginfo[localseg].dest_seg;
		}

		hr->e.segment = seg;	
		hr->e.offset += offset;
		rdfaddheader(rdfheader, hr);
		break;

	    case 6: /* segment fixup */
		/*
		 * modify the segment numbers if necessary, and
		 * pass straight through to the output module header
		 *
		 * *** FIXME ***
		 */
		if (hr->r.segment == 2) {
		    fprintf(stderr, "%s: segment fixup in BSS section\n",
			    cur->name);
		    errorcount++;
		    break;
		}
		localseg = rdffindsegment(&cur->f, hr->r.segment);
		if (localseg == -1) {
		    fprintf(stderr, "%s: segment fixup in unrecognised"
			    " segment (%d)\n", cur->name, hr->r.segment);
		    errorcount++;
		    break;
		}
		hr->r.segment = cur->seginfo[localseg].dest_seg;
		hr->r.offset += cur->seginfo[localseg].reloc;

		if (!get_seglocation(&segs, hr->r.refseg, &seg, &offset))
		{
		    fprintf(stderr, "%s: segment fixup to undefined "
			    "segment %04x\n", cur->name, (int)hr->r.refseg);
		    errorcount++;
		    break;
		}
		hr->r.refseg = seg;
		rdfaddheader(rdfheader, hr);
		break;
	    }
	}

	free(header);
	done_seglocations(&segs);

   }

    /*
     * combined BSS reservation for the entire results
     */
    newrec.type = 5;
    newrec.b.reclen = 4;
    newrec.b.amount = bss_length;
    rdfaddheader(rdfheader, &newrec);

    /*
     * Write the header
     */
    for (i = 0; i < nsegs; i++)
    {
	if (i == 2) continue;
	rdfaddsegment (rdfheader, outputseg[i].length);
    }
    rdfwriteheader(f, rdfheader);
    rdfdoneheader(rdfheader);
    /*
     * Step through the segments, one at a time, writing out into
     * the output file
     */
    
    for (i = 0; i < nsegs; i++)
    {
	int16 s;
	long l;
	
	if (i == 2) continue;

	s = translateshort(outputseg[i].type);
	fwrite(&s, 2, 1, f);
	s = translateshort(outputseg[i].number);
	fwrite(&s, 2, 1, f);
	s = translateshort(outputseg[i].reserved);
	fwrite(&s, 2, 1, f);
	l = translatelong(outputseg[i].length);
	fwrite(&l, 4, 1, f);

	fwrite(outputseg[i].data, outputseg[i].length, 1, f);
    }

    fwrite("\0\0\0\0\0\0\0\0\0\0", 10, 1, f);
}

/* =========================================================================
 * Main program
 */

void usage()
{
    printf("usage:\n");
    printf("   ldrdf [options] object modules ... [-llibrary ...]\n");
    printf("   ldrdf -r\n");
    printf("options:\n");
    printf("   -v[=n]    increases verbosity by 1, or sets it to n\n");
    printf("   -a nn     sets segment alignment value (default 16)\n");
    printf("   -s        strips exported symbols\n");
    printf("   -x        warn about unresolved symbols\n");
    printf("   -o name   write output in file 'name'\n");
    printf("\n");
    printf("Note: no library searching is performed. Please specify full\n");
    printf("paths to all files referenced.\n");
    exit(0);
}

int main(int argc, char ** argv)
{
    char * outname = "aout.rdf";
    int  moduleloaded = 0;

    options.verbose = 0;
    options.align = 16;
    options.warnUnresolved = 0;
    options.strip = 0;
    
    argc --, argv ++;
    if (argc == 0) usage();
    while (argc && **argv == '-' && argv[0][1] != 'l')
    {
	switch(argv[0][1]) {
	case 'r':
	    printf("ldrdf (linker for RDF files) version " LDRDF_VERSION "\n");
	    printf( _RDOFF_H "\n");
	    exit(0);
	case 'v':
	    if (argv[0][2] == '=') {
		options.verbose = argv[0][3] - '0';
		if (options.verbose < 0 || options.verbose > 9) {
		    fprintf(stderr, "ldrdf: verbosity level must be a number"
			    " between 0 and 9\n");
		    exit(1);
		}
	    }
	    else
		options.verbose++;
	    break;
	case 'a':
	    options.align = atoi(argv[1]);
	    if (options.align <= 0) {
		fprintf(stderr, 
			"ldrdf: -a expects a positive number argument\n");
		exit(1);
	    }
	    argv++, argc--;
	    break;
	case 's':
	    options.strip = 1;
	    break;
	case 'x':
	    options.warnUnresolved = 1;
	    break;
	case 'o':
	    outname = argv[1];
	    argv++, argc--;
	    break;
	default:
	    usage();
	}
	argv++, argc--;
    }

    if (options.verbose > 4) {
	printf("ldrdf invoked with options:\n");
	printf("    section alignment: %d bytes\n", options.align);
	printf("    output name: `%s'\n", outname);
	if (options.strip)
	    printf("    strip symbols\n");
	if (options.warnUnresolved)
	    printf("    warn about unresolved symbols\n");
	printf("\n");
    }

    symtab = symtabNew();
    initsegments();

    if (!symtab) {
	fprintf(stderr, "ldrdf: out of memory\n");
	exit(1);
    }

    while (argc)
    {
	if (!strncmp(*argv, "-l", 2)) /* library */
	    add_library(*argv + 2);
	else {
	    loadmodule(*argv);
	    moduleloaded = 1;
	}
	argv++, argc--;
    }

    if (! moduleloaded) {
	printf("ldrdf: nothing to do. ldrdf -h for usage\n");
	return 0;
    }

    
    search_libraries();

    if (options.verbose > 2)
    {
	printf ("symbol table:\n");
	symtabDump(symtab, stdout);
    }

    write_output(outname);

    if (errorcount > 0)
	exit(1);

    return 0;
}